D-cycloserine enhances short-delay, but not long-delay, conditioned taste aversion learning in rats.
NMDA receptors have been implicated in conditioned taste aversion (CTA), a form of associative learning with the unique temporal characteristic of associating taste and toxic stimuli across very long delays. d-cycloserine (DCS), an NMDA receptor agonist, has been shown to enhance short-delay CTA learning. Here we examined the interaction of DCS with varying temporal parameters of CTA. DCS (15 mg/kg) administered prior to the pairing of 0.125% saccharin and LiCl (38 mM, 12 ml/kg) enhanced CTA when there was a short delay between the taste-toxin pairing (10 min), but not when there was a long delay (45 min). DCS activity remained at effective levels over the long delay, because DCS administered 60 min prior to a short-delay pairing enhanced CTA. The interaction of DCS with the delay between taste stimulus onset and LiCl injection was investigated by administering DCS and then 5 min access to saccharin 45 min prior to a short-delay pairing of saccharin and LiCl. DCS failed to enhance CTA in rats pre-exposed to saccharin, even with a short delay between the second saccharin exposure and LiCl injection. These results suggest that DCS enhancement of CTA is dependent on mechanisms underlying gustatory processing during long-delay taste-toxin associations.
Davenport
Rachel A
RA
Program in Neuroscience, Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
Houpt
Thomas A
TA
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects*; D003523:Cycloserine / Q000494:pharmacology*; D005998:Glycine / Q000494:pharmacology; D018021:Lithium Chloride / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects; D012055:Reinforcement Schedule; D013649:Taste / Q000187:drug effects*; D013997:Time Factors
D016194:Receptors, N-Methyl-D-Aspartate; D003523:Cycloserine; D018021:Lithium Chloride; D005998:Glycine